DE69717020T2 - Flaky layered materials and nano-compositions containing such materials with attached water-insoluble oligomers or polymers - Google Patents

Abstract

A phyllosilicate material is exfoliated by admixture of the phyllosilicate with water, and a solvent for a water-insoluble oligomer or polymer that is sorbed or electrostatically bonded to the inner surfaces of the phyllosilicate platelets after exfoliation of the phyllosilicate. Intercalation and exfoliation can be achieved via contact of the phyllosilicate with an organic solvent and water to electrostatically bond one or more polar moieties from the organic solvent to a metal cation on the platelet inner surfaces, so that after evaporation of the water used for intercalation of the organic solvent between phyllosilicate platelets, the platelets do not then collapse together, but remain exfoliated. -After exfoliation of the phyllosilicate, the exfoliated platelets are contacted with a polymer/carrier composition that includes a water-insoluble polymer or water-insoluble oligomer, and a solvent for the water-insoluble polymer or oligomer. After exfoliating the phyllosilicate and prior to polymer contact, the individual phyllosilicate platelets are contacted with the polymer/carrier composition to sorb the water-insoluble polymer or water-insoluble oligomer onto one or both surfaces of the exfoliated phyllosilicate platelets and drive off the adhered solvent.

Description

The present invention relates to exfoliated layered materials prepared by sorption (adsorption and/or absorption) of one or more water-insoluble oligomers or polymers onto exfoliated platelets of a water-swellable layered material, such as a phyllosilicate or another layered material. The present invention particularly relates to exfoliated phyllosilicate platelets having at least one layer of oligomer and/or polymer molecules sorbed onto the outer surface of exfoliated planar platelets of a layered material, such as a phyllosilicate, preferably a smectite clay. The resulting polymer or oligomer/platelet is neither completely organophilic nor completely hydrophilic, but a combination of both. The polymer or oligomer is held to the phyllosilicate platelets by an electrostatic bond and can be blended with a thermoplastic or thermosetting matrix polymer melt, preferably a thermoplastic matrix polymer, to improve one or more properties of the matrix polymer. The resulting matrix polymer/platelet composites are useful wherever polymer/filler composites are used, such as as external body panels for the automotive industry; heat resistant polymer automotive parts in contact with an engine block; tire cords for radial tires; food packaging with improved gas impermeability; electrical components: food grade beverage containers; and many other applications where altering one or more physical properties of a matrix polymer, such as elasticity and temperature characteristics such as glass transition temperature and resistance to high temperatures, is desired.

BACKGROUND OF THE INVENTION AND STATE OF THE ART

It is widely known that phyllosilicates, such as smectite clays, such as sodium montmorillonite and calcium montmorillonite, react with organic Molecules, such as organic ammonium ions, to intercalate the organic molecules between adjacent planar silicate layers, thereby significantly increasing the interlayer space (interlaminar space) between the adjacent silicate layers. The intercalated phyllosilicates treated in this way, with interlayer spaces of at least about 5 Angstroms, preferably at least about 10-20 Angstroms and up to about 100 Angstroms, can then be exfoliated, for example the silicate layers are separated mechanically by high shear mixing, for example. It has been found that when the individual silicate layers are admixed with a matrix polymer before, after or during polymerization of the matrix polymer, such as a polyamide - see US 4,739,007; US 4,810,734 and US 5,385,776 - they significantly improve one or more properties of the polymer, such as mechanical strength and/or high temperature characteristics.

Examples of such prior art composites, also referred to as "nanocomposites," are disclosed in Allied Signal, Inc.'s published PCT disclosure WO 93/04118 and U.S. Patent No. 5,385,776, which disclose admixing individual platelet particles derived from intercalated layered silicate materials with a polymer to form a polymer matrix having one or more properties of the matrix polymer that are enhanced by the addition of the exfoliated intercalate. As disclosed in WO 93/04118, the intercalate is formed by adsorption of a silane coupling agent or an onium cation, such as a quaternary ammonium compound, having a reactive group compatible with the matrix polymer (the interlayer space between adjacent silicate platelets is increased). Such quaternary ammonium cations are widely known to convert a highly hydrophilic clay, such as sodium or calcium montmorillonite, into an organophilic clay capable of sorbing organic molecules. A publication disclosing the direct intercalation (without solvent) of polystyrene and poly(ethylene oxide) in organically modified silicates is Synthesis and Properties of Two-Dimensional Nanostructures by Direct Intercalation of Polymer Melts in Layered Silicates, Richard A. Vaia, et al. Chem. Mater., 5: 1694-1696 (1993). Also as in Adv, Materials, 7, no. 2: (1985), pp. 154-156, New Polymer Electrolyte Nanocomposites: Melt Intercalation of Poly(ethylene Oxide) in Mica-Type Silicates, Richard A. Vaia et al. disclosed, poly(ethylene oxide) can be directly intercalated to Na-montmorillonite and Li-montmorillonite by heating at 80°C for 2 to 6 hours to achieve a d-space of 17.7 Å. The intercalation is accompanied by displacement of water molecules deposited between the clay platelets with polymer molecules. Apparently, however, the intercalated material could not be exfoliated and was tested in pellet form. It was quite surprising to one of the authors of these articles that exfoliated material could be produced according to the invention.

Previous attempts have been made to intercalate water-soluble polymers such as polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and poly(ethylene oxide) (PEO) between montmorillonite clay platelets with little success. As in Levy, et al., Inlerlayer Adsorption of Polyvinylpyrrolidone on Montmorillonite, Journal of Colloid and Interface Science. Vol. 50, No. 3, March 1975, pages 442-450, attempts were made to sorb PVP (average MW 40,000) between monoionic montmorillonite clay platelets (Na, K, Ca and Mg) by successive washing with absolute ethanol and then attempting to sorb the PVP by contact with 1% PVP/ethanol/water solutions, with various amounts of water, by replacing the ethanol solvent molecules sorbed during washing (to expand the platelets to ca. 17.7 Å). Only the sodium montmorillonite had expanded beyond a basal interspace of 20 Å (such as 26 Å and 32 Å) at 5% H₂O after contact with the PVP/ethanol/H₂O solution. It was concluded that the ethanol was needed to initially enlarge the basal interspace for subsequent sorption of PVP and that water did not directly affect the sorption of PVP between the clay platelets (Table II, page 445), except for sodium montmorillonite. Sorption was time consuming and difficult and met with little success.

As further described in Greenland, Adsorption of Polyvinyl Alcohols by Montmorillonite, Journal of Colloid Sciences, Vol. 18, pp. 647-664 (1963), polyvinyl alcohols containing 12% residual acetyl groups were only able to increase the basal space due to the sorted polyvinyl alcohol (PVOH) by about 10 Å. As the polymer concentration in the intercalating polymer-containing solution was increased from 0.25% to 4%, the amount of polymer sorbed was significantly reduced, suggesting that sorption could only be effective at polymer concentrations in the intercalating polymer-containing composition on the order of 1% polymer by weight or less. Such a dilution process for intercalating polymer into layered materials would be exceptionally costly in drying the intercalated layered materials to separate the intercalate from the polymer carrier, such as water, and therefore no further work toward commercialization appears to have been completed.

In accordance with an important feature of the invention, it has been found that it is best to exfoliate the phyllosilicate prior to contacting the phyllosilicate with a polymer or oligomer to provide polymer or oligomer bound platelets that do not include a substantial amount of unexfoliated phyllosilicate clumps or tactoids. Best results are achieved using a composition of water-insoluble oligomer (defined herein as a prepolymer having from 2 to about 15 repeating monomeric units, which may be the same or different) or water-insoluble polymer (defined herein as having more than about 15 repeating monomeric units, which may be the same or different) for intercalation with a minimum of about 2 wt.%, preferably at least about 5 wt.% oligomer or polymer concentration, more preferably about 50 wt.% to about 80 wt.% oligomer and/or polymer based on the weight of oligomer and/or polymer and carrier (water and a solvent for the oligomer or polymer) to achieve better sorption of the polymers or oligomers to the outer surfaces of the exfoliated phyllosilicate platelets. The water-insoluble oligomer or polymer is sorbed to at least one outer surface of the silicate platelets.

A phyllosilicate, such as a smectite clay, can be easily and completely exfoliated by adding water and an organic solvent having a polar functionality and then shearing the phyllosilicate/water/solvent mixture. After exfoliation, it has been found that a water-insoluble polymer and/or a water-insoluble oligomer can adhere to the outer surfaces of the exfoliated platelets as long as the polymer or oligomer has a carbonyl, hydroxyl, carboxyl, amine, amide, ether, ester, sulfate, sulfonate, sulfinate, sulfamate, phosphate, phosphonate or phosphinate functionality, or an aromatic ring to provide metal cation bonding to the outer surfaces of the exfoliated phyllosilicate platelets via a metal cation of the phyllosilicate that shares electrons with two electronegative atoms of two functional groups of the polymer molecules. The electronegative atoms may be, for example, oxygen, sulfur, nitrogen, and combinations thereof. Atoms having sufficient electronegativity to bind to metal cations on the inner surface of the platelets have an electronegativity of at least 2.0, and preferably at least 2.5 on the Pauling scale. A "polar component" or "polar group" is defined as a component having two adjacent atoms that are covalently bonded and have a difference in electronegativity of at least 0.5 electronegativity units on the Pauling scale. Such polymers have sufficient affinity to the phyllosilicate platelets to maintain sufficient interlayer space for exfoliation without the need for coupling agents or spacing agents, such as the onium ion or silane coupling agents disclosed in the above-mentioned prior art. A schematic representation of the charge distribution on the Surfaces of a sodium montmorillonite clay are shown in Fig. 1-3. As shown in Fig. 2 and 3, the location of Na+ surface cations on the surface with respect to the location of O, Mg, Si and Al atoms (Fig. 1 and 2) results in a charge distribution on the clay surface as shown schematically in Fig. 3. The positive-negative charge distribution over the entire clay surface provides excellent dipole/dipole attraction of the polar components of the polymer molecules on the surfaces of the clay platelets.

Sorption and electrostatic attraction of metal cations or bonding of a platelet metal cation between two oxygen or nitrogen atoms of the polymer or oligomer molecules [sic]; or electrostatic bonding between the interlayer cations in six- or pseudo-six-membered rings of the smectite platelet layers or an aromatic ring structure of the oligomer or polymer provides a tightly adherent bond between the polymer or oligomer and the outer surface of the exfoliated silicate platelets or other layered material, while providing individual silicate/polymer nanocomposite material and without including a substantial amount of non-exfoliated clumps or tactoids of phyllosilicate material. Phyllosilicates can be readily exfoliated into individual phyllosilicate platelets prior to admixture with a polymer or oligomer, as is well known in the art.

DEFINITIONS

Whenever used in this description, the terms set out have the following meaning:

"Layered material" means an inorganic material, such as a smectite clay material, that is, in the form of a plurality of adjacent, bonded layers and having a maximum thickness for each layer of approximately 100 Å.

"Plates" mean individual layers of the layered material.

"Intercalate" or "intercalated" means a layered material that includes water molecules deposited between adjacent platelets of the layered material to increase the interlayer spacing between the adjacent platelets to at least 10 Å.

"Intercalation" means a process for forming an intercalate.

"Intercalating composition" means a composition comprising water and an organic solvent capable of dissolving a subsequently added water-insoluble oligomer or polymer.

"Exfoliate" or "exfoliated" means individual platelets of an intercalated layered material such that adjacent platelets of the intercalated layered material can be individually dispersed for sorption of a water-insoluble polymer or oligomer.

"Exfoliation" means a process for forming an exfoliate from an intercalate.

"Nanocomposite" means an oligomer, polymer or copolymer having a plurality of individual platelets dispersed therein obtained from an exfoliated oligomer-sorbed or polymer-sorbed layered material.

"Matrix polymer" means a thermoplastic or thermosetting polymer in which the oligomer-sorbed or polymer-sorbed exfoliate is dispersed to form a nanocomposite.

"Polymer/carrier composition" means a composition containing a water-insoluble polymer and/or a water-insoluble oligomer; a solvent capable of solubilizing the polymer and/or oligomer; and water.

"Tactoid" means a package of two or more platelet layers of intercalated Sound that acts as a unit.

SUMMARY OF THE INVENTION

Briefly, the present invention is directed to exfoliated platelets of a phyllosilicate material which are exfoliated by admixing the phyllosilicate with water and a solvent for a water-insoluble oligomer or polymer which is sorbed or electrostatically bonded to the inner surfaces of the phyllosilicate platelets after exfoliation of the phyllosilicate. Intercalation and exfoliation can be achieved by contacting the phyllosilicate with an organic solvent and water to electrostatically bond a polar component or components from the organic solvent to a metal cation on the inner surfaces of the platelets, so that after evaporation of the water used to intercalate the organic solvent between phyllosilicate platelets, the platelets do not collapse but remain exfoliated. The organic solvent used should be capable of dissolving at least a portion of the water-insoluble polymer added later; must be capable of sufficiently intercalating between phyllosilicate platelets, together with water, for subsequent exfoliation of the phyllosilicate platelets, if necessary under shearing; and must be sufficiently electrostatically bonded to the inner surfaces of the exfoliated clay platelets to maintain the platelets in the exfoliated state after dehydration of the exfoliated platelet/solvent/water composition. Suitable solvents include... γ-butyrolactone; 2-pyrrolidone; n-methylpyrrolidone; dimethyl sulfoxide (DMSO); isophorone; diglyme (diethylene glycol dimethyl ether); caprolactam; furfuryl alcohol; tetrahydrofuran, and mixtures thereof.

After exfoliation of the phyllosilicate, the exfoliated platelets are contacted with a polymer/carrier composition including a water-insoluble polymer or water-insoluble oligomer and a solvent for the water-insoluble polymer or oligomer. After exfoliation of the phyllosilicate and prior to polymer contact, the individual phyllosilicate platelets are contacted with the polymer/carrier composition to sorb the water-insoluble polymer or water-insoluble oligomer to one or both surfaces of the exfoliated phyllosilicate platelets and drive off the adhering solvent. Sufficient polymer is sorbed to the surface(s) of the phyllosilicate platelets to provide at least one molecular layer of polymer or oligomer over at least one exposed platelet surface of each platelet.

The organic solvent sorbed to the surfaces of the phyllosilicate platelets should have an affinity for the phyllosilicate such that it is sorbed thereto and maintained in association with the silicate platelet surfaces until the exfoliated platelets are contacted with a water-insoluble polymer melt in a solvent for the water-insoluble polymer. According to the invention, the organic solvent should include an aromatic ring and/or have a functionality selected from the group consisting of carbonyl; carboxyl; hydroxyl; amide; ether or ester to be sufficiently bound to the surface of the phyllosilicate platelets. It is hereby theorized that the solvent is bound to the inner surface of the phyllosilicate platelets by a mechanism selected from the group consisting of metal cation binding or complex formation, such as chelation; ionic complex formation; electrostatic complex formation; hydrogen bonding; dipole/dipole; Van der Waal forces and any combination thereof such that a metal cation of a phyllosilicate shares electrons with two carbonyl, two carboxyl, two hydroxyl, two oxygen, two ether, two ester, two aromatic ring and/or two amide functionalities of one or two organic solvent molecules. Such organic solvents have sufficient affinity to the surfaces of the phyllosilicate platelets to be sufficiently bound to the surfaces of the phyllosilicate platelets without the need for coupling agents or spacing agents such as the onium ion or silane coupling agents described in the above-mentioned State of the art should be mentioned.

The sorption of the organic solvent should be sufficient to achieve expansion of adjacent platelets of the layered material (when measured dry) to an interlayer spacing of at least about 5 Å, preferably at least about 10 Å, more preferably a spacing of at least about 20 Å, and most preferably a spacing of about 30-45 Å. To achieve sufficient sorption of the water-insoluble polymer or oligomer to the basal surface of the exfoliated phyllosilicate platelets, the concentration of organic solvent in the organic solvent/water intercalating composition contacting the phyllosilicate should be at least about 2 wt.%, preferably at least about 5 wt.%, more preferably at least 15 wt.%, and most preferably at least about 20 wt.% organic solvent, for example about 25% to about 100 wt.% organic solvent based on the dry weight of the phyllosilicate contacted by the intercalating composition.

Such intercalation of organic solvent polymer molecules between platelets of a phyllosilicate such that the phyllosilicate can be readily exfoliated and the exfoliation can be maintained even after water removal. It has further been found that more complete exfoliation of the phyllosilicate is achieved if the phyllosilicate is exfoliated prior to contact with the polymer or oligomer. Such organic solvent sorbed platelets are particularly useful in admixture with thermoplastic or thermosetting matrix polymer melts in the manufacture of polymeric articles containing the exfoliated platelets because the exfoliated platelets do not collapse back into the original layered structure of the phyllosilicate when added to the polymer melt resulting in dehydration of the exfoliated platelets; and for admixing the exfoliated polymer or oligomer sorbed platelets with polar solvents in rheology modification, such as cosmetics, oil drilling fluids, in the manufacture of oil and grease, and the like.

To achieve the full benefit of the present invention, a gel containing the phyllosilicate is prepared by mixing the phyllosilicate with water and an organic solvent having a polar functionality such as: an aromatic ring; a carboxyl; carbonyl; hydroxyl; amide; ether or ester such that a metal cation of the phyllosilicate shares electrons with two carboxyl, two carbonyl, two hydroxyl, two oxygen, two ether, two ester, two aromatic ring and/or two amide functionalities of one or two organic solvent molecules. The combination of water and organic solvent is capable of intercalating between phyllosilicate platelet layers to sufficiently space the layers between such that the platelets are separated predominantly into a predominance of individual layers and tactoids including 1 phyllosilicate platelet to 5 stacked phyllosilicate platelets, predominantly a combination of individual platelets and tactoids having 2 to about 4 platelet layers that are electrostatically bonded to the inner surfaces of the platelets with organic solvent.

The organic solvent used to form the phyllosilicate-containing gel (Gel A of the Examples) should either be sufficiently compatible with water to form an emulsion with water, or a co-solvent may be added to produce the combination of water and organic solvents sufficiently compatible to allow the mixture to be sheared with the phyllosilicate into a thixotropic gel. The organic solvent used to form the gel should preferably have a boiling point above about 75°C such that after heating the gel to a temperature of about 100°C-130°C, the gel can be dehydrated without total loss of organic solvent from the gel. However, the electrostatic binding of the organic solvent to the inner surfaces of the phyllosilicate platelets significantly increases the energy required to separate the solvent from the phyllosilicate surfaces, such that almost any organic solvent containing one or more of the above-mentioned functionalities can be used to induce the gel. works and remains fixed to the platelet surface(s) after dehydration of the gel.

After gel formation and dehydration of the gel, the predominantly individual platelets and tactoids of 2-4 platelet layers have the organic solvent bound to the inner surfaces of the platelets in such a way that dehydration does not cause the collapse of the platelets into a layered structure with more than 5 platelets stacked on top of each other.

The gel is then mixed with a water insoluble polymer and a solvent for the water insoluble polymer, and the polymer is melted by heating the mixture to a temperature sufficient to melt the polymer. It has been found that when the polymer is dissolved with a solvent and mixed with the gel, the melting temperature is reduced by approximately 5-20°C below its solid melting temperature. Preferably, at least one of the organic solvents used to dissolve the water insoluble polymer is the same as the organic solvent used to form the phyllosilicate gel to ensure solution compatibility. Should the polymer-dissolving solvent be different from the gel-forming solvent, then the two solvents should be compatible, or a co-solvent may be added for the purpose of providing a compatible mixture of water and organic solvents which, together with the phyllosilicate platelets and tactoids, will evaporate during mixing and heating during sequential evaporation of the water; melting the polymer and then evaporating the organic solvents to leave a thixotropic gel. As shown in Example 1 below, the addition of a co-solvent such as methyl ethyl ketone (MEK) aids in the dehydration of the gel, it is theorized, by forming an azeotrope with the water when enough water has been evaporated to form an azeotropic mixture of water and MEK. However, provided that sufficient time is allowed for water evaporation, the gel can be essentially completely dehydrated to less than about 1 wt.% water without forming an azeotropic composition with an organic solvent. The preferred compatibilizing solvents for use with polymer dissolving solvents that are not compatible with water are selected from the group consisting of g-butyrolactone -

γ-butyrolactone and diglyme (CH₃-O-CH₂-CH₂-O-CH₂-CH₂-O-CH₃) and γ-butyrolactone, diglyme and methyl ethyl ketone.

For example, when added to a matrix polymer, the organic solvent-sorbed platelets are predominantly completely separated or exfoliated into individual platelets or contain a predominance of a combination of individual platelets and tactoids containing an average number of stacked platelets numbering 4 or less, preferably 3 or 1. Once exfoliated, the originally adjacent platelets are no longer retained in or collapse back into tactoids comprising a parallel, spaced-apart deposit of 5 or more platelets, but are free to move as predominantly individual platelets and 2-4 platelet tactoids throughout a matrix polymer melt, even after dehydration, to act similarly to a nanoscale filler for the matrix polymer. Once combined with a matrix polymer, the water-insoluble polymer molecules displace the relevant molecules and the composite material sets and is cured into a desired shape, the individual polymer-sorbed or oligomer-sorbed phyllosilicate platelets are permanently fixed in position and become randomly, homogeneously and uniformly dispersed, predominantly as individual platelets, throughout the matrix polymer/platelet composite material.

As seen, the thickness of the exfoliated organic solvent sorted individual platelets (ca. 5-10 Å) is relatively small compared to the size of the flat opposing platelet faces. The platelets have an aspect ratio in the range of ca. 200 to ca. 4000. Dispersing such finely divided platelet particles in a polymer melt provides a very large contact area between polymer and platelet particles for a given particle volume in the composite and a high degree of platelet homogeneity in the composite. Furthermore, since the polymer melts are at temperatures that evaporate the water used for solvent intercalation, the platelets in the polymer melt are dehydrated but, surprisingly, do not collapse back to their original phyllosilicate structure (exfoliation is maintained).

While the nanocomposites disclosed in WO 93/04118 require a swelling/compatibilizing agent, such as a silane coupling agent, or a quaternary ammonium molecule that has distinct bonding interactions with both the polymer and the platelet particle to achieve improved properties in the polymer, the polymer-loaded exfoliated platelets prepared according to the invention do not need to have a coupling agent for the intercalation and sorption of the organic solvent molecules or for the polymer or oligomer molecules that are later bound to the surfaces of the phyllosilicate platelets.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic representation of a top view of sodium montmorillonite clay showing the ionic charge distribution for the surfaces and interlayer areas of the sodium montmorillonite clay showing both Na' ions as the largest circles and magnesium and aluminum ions and Si and oxygen (Ox) atoms deposited beneath the sodium ions;

Fig. 2 is a side view (bc projection) of the schematic representation of Fig. 1;

Fig. 3 is a schematic representation of the charge distribution on the surfaces of sodium montmorillonite clay platelets, showing the distribution of positive and negative charges on the clay platelet surfaces due to the natural deposition of the Na, Mg, Al, Si and O atoms of the clay shown in Figs. 1 and 2;

Figure 4 is an X-ray diffraction pattern for a complex of sodium montmorillonite clay and polypropylene prepared according to Example 1;

Figure 5 is an X-ray diffraction pattern for the gel prepared according to Example 2 showing complete exfoliation of the clay platelets;

Figure 6 is an X-ray diffraction pattern for a complex of sodium montmorillonite clay and ethylene-vinyl alcohol polymer prepared according to Example 2;

Figure 7 is an X-ray diffraction pattern for a complex of sodium montmorillonite clay and ethylene-vinyl alcohol polymer prepared according to Example 3;

Fig. 8 is an X-ray diffraction pattern for a mixture of sodium montmorillonite clay and ethylene-vinyl alcohol polymer prepared according to Example 4; and

Figure 9 is an X-ray diffraction pattern for a mixture of sodium montmorillonite clay and ethylene-vinyl alcohol polymer prepared according to Example 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To form the composite materials of the present invention, the phyllosilicate should be first intercalated with water and an organic solvent, then exfoliated, and finally the exfoliated platelets should be contacted with a water-insoluble polymer/carrier composition that includes a solvent for the water-insoluble polymer or oligomer. The water-insoluble oligomer or polymer should include an aromatic ring and/or functionality selected from the group consisting of: carbonyl; carboxyl; hydroxyl; amine; amide; ether; ester; sulfate; sulfonate; sulfinate; sulfamate; phosphate; phosphonate or phosphinate functionality; or an aromatic ring or combinations thereof.

Intercalation and exfoliation are achieved by mixing the phyllosilicate with water and a solvent for a later added water-insoluble oligomer or polymer. The organic solvent is intercalated between phyllosilicate platelets and is adhered to the inner surfaces of the platelets, it is theorized, by binding a polar component or components from the organic solvent to a metal cation on the platelet inner surface such that after evaporation of the water used to intercalate the organic solvent between the phyllosilicate platelets, the platelets then do not collapse together but remain exfoliated. The organic solvent used should be capable of dissolving at least a portion of the later added water-insoluble polymer; must be capable of sufficiently intercalating between phyllosilicate platelets, together with water, for subsequent exfoliation of the phyllosilicate platelets, if necessary under shear; and must be sufficiently electrostatically bonded to the inner surfaces of the exfoliated clay platelets to maintain the platelets in the exfoliated state following dehydration of the exfoliated platelet/solvent/water composition.

The organic solvent sorbed to the surfaces of the phyllosilicate platelets should have an affinity for the phyllosilicate such that it is sorbed to the surfaces of the silicate platelets and maintained associated with them until the exfoliated platelets are heated to a temperature sufficient to release the organic solvent from the platelets or until the platelets are contacted with a water-insoluble polymer melt and a solvent for the water-insoluble polymer. According to the invention, the organic solvent should include an aromatic ring and/or have a functionality selected from the group consisting of: a carbonyl; carboxyl; hydroxyl; amide; ether or ester functionality. It is hereby theorized that the solvent is bound to the inner surface of the phyllosilicate platelets by a mechanism selected from the group consisting of: metal cation binding or complexing, such as chelation; ionic complexing; electrostatic complexing; hydrogen bonding; dipole/dipole; van der Waals forces; and any combination thereof such that a metal cation from a phyllosilicate shares electrons with two carbonyl, two carboxyl, two hydroxyl, two oxygen, two ether, two ester, two aromatic ring and/or two amide functionalities from one or two organic solvent molecules. Such organic solvents have sufficient affinity to the surfaces of the phyllosilicate platelets to remain sufficiently bound to the surfaces of the phyllosilicate platelets without the need for coupling agents or spacing agents, such as the onium ion or silane coupling agent disclosed in the above-mentioned prior art.

Exemplary solvents include: dimethyl sulfoxide (DMSO); isophorone; γ-butyrolactone; n-methylpyrrolidone: 2-pyrrolidone; diglyme; caprolactam; furfural alcohol; tetrahydrofuran, and mixtures thereof.

According to a preferred embodiment of the present invention, the amount of polymer or oligomer in contact with the exfoliated phyllosilicate platelets should have a weight ratio of polymer or oligomer/phyllosilicate platelets (based on the dry weight of the phyllosilicate) of at least 10/100, preferably at least about 16/100, and more preferably about 20-70/100, to provide sufficient sorption of the water-insoluble polymer or water-insoluble oligomer to the exfoliated platelets of the layered material, such as phyllosilicate (preferably about 16 to about 70 weight percent polymer or oligomer based on the dry weight of the layered silicate material).

The water-insoluble polymers and oligomers are solubilized in the polymer/carrier composition, and the polymer and/or oligomer should be included in the composition in an amount sufficient to provide a polymer or oligomer concentration of at least about 2%, preferably at least about 5%, by weight of polymer or oligomer, more preferably at least about 50% to about 100% by weight of polymer or oligomer in the polymer/carrier composition. The polymer can be added as a solid with the addition to the polymer/carrier composition of about 20% to about 80% polymer solvent.

Any swellable layered material which adequately sorbs the polymer or oligomer can be used in the practice of this invention. Useful swellable layered materials include phyllosilicates such as smectite clay minerals such as montmorillonite, particularly sodium montmorillonite; magnesium montmorillonite; and/or calcium montmorillonite; nontronite; beidellite; volkonskoite; hectorite; saponite; sauconite; sobockite; stevensite; svinfordite; vermiculite, and the like. Other useful layered materials include micaceous minerals such as illite and mixed layered illite/smectite minerals such as ledikites and admixtures of caps with the above-mentioned clay minerals. Preferred swellable layered materials are phyllosilicates of the 2:1 type with a negative charge on the layers ranging from about 0.15 to about 0.9 charges per formula unit and a corresponding number of exchangeable metal cations in the interlayer spaces. The most preferred layered materials are smectite clay minerals such as montmorillonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, sobockite, stevensite and svinfordite.

The amount of water-insoluble polymer or oligomer sorbed to the surfaces of the exfoliated platelets of the layered materials useful in this invention can vary considerably between about 15% and about 80% based on the dry weight of the exfoliated platelets of the layered silicate material. In the preferred embodiments of the invention, amounts of polymer or oligomer employed based on the dry weight of exfoliated platelets of the layered material preferably range from about 16 g polymer or oligomer/100 g layered material (dry basis) to about 80 g polymer or oligomer/100 g exfoliated platelets. More preferred amounts range from about 20 g polymer or oligomer/100 g exfoliated platelets to about 60 g polymer or oligomer/100 g exfoliated platelets (dry basis).

The polymers and oligomers are bound (sorbed) to the surface of the platelets as follows. In a preferred sorption process, the exfoliated platelets of a layered material are intimately mixed, such as by extrusion, with a concentrated polymer/carrier composition containing the polymer and/or oligomer; water; and a solvent for the polymer, such as an organic solvent such as alcohols, esters, ketones, ethers, alkyl amides, aromatic solvents, glycols, and the like. To achieve sufficient sorption of the polymer or oligomer to the platelet surfaces, the exfoliated platelets of the layered material/polymer/carrier composition contain at least about 16% by weight of polymer or oligomer based on the dry weight of the exfoliated platelets of the layered material.

The polymer carrier (an organic solvent for the polymer or oligomer) can be added by first solubilizing or dispersing the polymer or oligomer in a suitable organic solvent carrier; or the dry Polymer or oligomer and exfoliated phyllosilicate platelets may be mixed and the polymer solvent may be added to the mixture or exfoliated phyllosilicate platelets prior to addition of the dry polymer or oligomer.

Alternatively, the polymer carrier, such as an organic solvent for the oligomer or polymer, can be added directly to the exfoliated phyllosilicate platelets prior to addition of the polymer or oligomer (either dry or in solution). Alternatively, the exfoliated platelets of the layered material can be added to liquid polymer or liquid oligomer melt compositions (solubilized with an organic solvent for the polymer or oligomer and heated to at least the melting temperature for the polymer or oligomer) containing at least about 2% by weight, preferably at least about 5% by weight polymer or oligomer, more preferably at least about 50% polymer or oligomer based on the total weight of the polymer/carrier composition (polymer plus organic solvent for the polymer). Sorption can be assisted by exposing the mixture of polymer/solvent composition and exfoliated platelets of the layered material to heat, pressure, ultrasonic cavitation or microwaves.

According to an important embodiment of the present invention, one or more polymerizable monomers can be sorbed to the exfoliated platelets of the layered material or simply admixed with the exfoliated layered material, and the polymerizable monomer(s) are polymerized while in contact with the exfoliated platelets. The polymerizable monomer(s) can be, for example, a mixture of a diamine and a dicarboxylic acid suitable for reaction to produce a polyamide, such as nylon; or the monomer(s) can be any of the polymerizable organic liquids which polymerize to form a water-insoluble polymer disclosed in U.S. Patent No. 4,251,576.

Suitable broad classes of water-insoluble polymers and oligomers include: polyamides; polyesters; polycarbonates; polyurethanes; polyepoxides; polyolefins; polyalkylamides and mixtures thereof. Suitable specific water-insoluble polymers and oligomers include:

Polyethers (polymers and copolymers) based on ethylene oxide, butylene oxide, propylene oxide, phenols and bisphenols;

Polyesters (polymers and copolymers) based on aliphatic and aromatic diols and aliphatic and aromatic dibasic acids;

Polyurethanes based on aliphatic and aromatic diisocyanates and aliphatic and aromatic diols;

Polyamides (polymers and copolymers) based on (1) aliphatic and aromatic diamines and aliphatic and aromatic dibasic acids; (2) aliphatic and aromatic amino acids; polycarbonates (polymers and copolymers) based on carboxylic acids and aromatic diols);

Polycarbonimides (polymers and copolymers) based on the dianhydride of tetrabasic acids and diamines and other heterochain polymers;

Vinyl polymers and copolymers based on vinyl monomers, styrene and styrene derivatives;

Acrylic polymers and copolymers based on acrylic monomers;

Copolymers based on styrene, vinyl and acrylic monomers;

Polyolefins, polymers and copolymers based on ethylene, propylene and other α-olefin monomers;

Polymers and copolymers based on dienes, isobutylenes and the like; and

Copolymers based on dienes, styrene, acrylic and vinyl monomers.

Thermosetting water-insoluble resins based on water-soluble prepolymers, including prepolymers based on formaldehyde: phenols (phenol, cresol and the like); urea; melamine; melamine and phenol; urea and phenol. Polyurethanes based on: toluene diisocyanate (TDI) and monomeric and polymeric diphenylmethane diisocyanates (MDI); hydroxy-terminated polyethers (polyethylene glycol, polypropylene glycol, copolymers of ethylene oxide and propylene oxide and the like); amino-terminated polyethers, polyamines (tetramethylenediamine, ethylenediamine, hexamethylenediamine, 2,2-dimethyl-1,3-propanediamine; melamine, diaminobenzene, triaminobenzene and the like); polyamidoamines (for example hydroxy-terminated polyesters); unsaturated polyesters based on maleic and fumaric anhydrides and maleic and fumaric acids; Glycols (ethylene, propylene), polyethylene glycols, polypropylene glycols, aromatic glycols and polyglycols; unsaturated polyesters based on vinyl, allyl and acrylic monomers; epoxides based on biphenol A (2,2'-bis(4-hydroxyphenyl)propane and epichlorohydrin; epoxy prepolymers based on monoepoxide and polyepoxide compounds and α,β-unsaturated compounds (styrene, vinyl, allyl, acrylic monomers); polyamides 4-tetramethylenediamine, hexamethylenediamine, melamine, 1,3-propanediamine, diaminobenzene, triaminobenzene, 3,3',4,4'-bitriaminobenzene;3,3'-4,4-biphenyltetramine and the like). Polyethylenimines; amides and polyamides (amides of di-, tri- and tetra-acids); Hydroxyphenols (pyrogallol, gallic acid, tetrahydroxybenzophenone, tetrahydroquinone, catechol, phenol and the like); anhydrides and polyanhydrides of di-, tri- and tetraacids; polyisocyanurates based on TDI and MDI; polyimides based on pyromellitic dianhydride and 1,4-phenyldiamine; polybenzimidozoles based on 3,3',4,4'-biphenyltetramine and isophthalic acid; polyamide based on unsaturated dibasic acids and anhydrides (maleic acid and fumaric acid) and aromatic polyamides; alkyd resins based on dibasic aromatic acids or anhydrides, glycerol, trimethylolpropane, pentaerythritol, sorbitol and unsaturated fatty long-chain carboxylic acids (the latter derived from vegetable oils); and prepolymers based on acrylic monomers (hydroxyl or carboxyl functional).

The amount of water-insoluble polymer or water-insoluble oligomer sorbed exfoliated platelets included in the matrix polymer to form the composite material can vary widely depending on the intended use of the composite. For example, relatively larger amounts of platelet particles (excluding the intercalating polymer, since the content of the intercalating polymer in the layered material can vary), i.e., from about 15% to about 30% by weight of the blend, can be used in applications where articles are formed by die cutting. Platelet particle concentrations greater than about 2.5% impart substantially improved barrier properties and thermal stability (deflection temperature under load (DTUL)). Similarly, substantially improved strength is imparted by concentrations of the platelet particles greater than about 1.5%, including the layered materials of this invention at the nanoscale. It is preferred that the loading of the platelets be less than about 10%. Loadings of the platelet particles in the range of about 0.05% to about 40%, preferably about 0.5% to about 20%, more preferably about 1% to about 10%, by weight of the composite material significantly improve modulus, dimensional stability, and wet strength. Generally, the amount of platelet particles incorporated into a matrix polymer is less than about 90 wt.% of the blend, and preferably from about 0.01 wt.% to about 80 wt.% of the composite blend, more preferably from about 0.05 wt.% to about 40 wt.% of the polymer/particle blend, and most preferably from about 0.05 wt.% to about 20 wt.% or 0.05 wt.% to about 10 wt.% with some matrix polymers.

According to an important feature of the present invention, the exfoliated platelets with adhering organic solvent can be used as concentrated platelets which contain solvent for a subsequently added water-insoluble polymer, such as 30 to 70 wt% platelets and 70 to 30 wt% solvent; or the exfoliated platelets may be prepared in a concentrated form, for example 10-90 wt%, preferably 20-80 wt% polymer and 10-90 wt%, preferably 20-80 wt% exfoliated phyllosilicate platelets, which may be dispersed in a matrix polymer.

The organic solvent treated phyllosilicate platelets can be dispersed in one or more melt processable thermoplastic and/or thermosetting matrix oligomers or polymers or mixtures thereof. Advantageously, the organic solvent coated platelets do not collapse upon water evaporation as would otherwise occur without the presence of the organic solvent adhering to the platelets. Matrix polymers for use in this inventive process can vary widely, the only requirement being that they be melt processable. In the preferred embodiments of the invention, the polymer includes at least 10, preferably at least 30, repeating monomer units. The upper limit for the number of repeating monomer units is not critical, provided that the melt index of the matrix polymer under conditions of use is such that the matrix polymer forms a flowable mixture. The matrix polymer most preferably includes from at least about 10 to about 100 repeating monomer units, for example having a weight average molecular weight in the range of 225 to 1,000,000 g/mol or in the range of 225 to 10,000 g/mol. In the most preferred embodiments of this invention, the number of repeating units is such that the matrix polymer has a melt index of from about 0.01 to about 12 g per 10 minutes at the processing temperature.

Thermoplastic resins and rubbers for use as matrix polymers and/or polymers or oligomers which can be bonded to the surfaces of exfoliated phyllosilicate platelets can be sorbed can vary widely in the practice of this invention. Illustrative of useful thermoplastic resins which can be used alone or in admixture are polylactones such as poly(pivalolactone), poly(caprolactone) and the like; polyurethanes derived from the reaction of diisocyanates such as: 1,5-naphthalene diisocyanate; p-phenylene diisocyanate, m-phenylene diisocyanate, 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 4,4'-diphenylisopropylidene diisocyanate, 3,3'-dimethyl-4,4'-diphenyl diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, dianisidine diisocyanate, toluidine diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanatodiphenylmethane and the like and linear long chain diols such as poly(tetramethylene adipate), poly(ethylene adipate), poly(1,4-butylene adipate), poly(ethylene succinate), poly(2,3-butylene succinate), polyether diols and the like; Polycarbonates such as poly[methane bis(4-phenyl)carbonate], poly[1,1-ether bis(4-phenyl)carbonate], poly[diphenylmethane bis(4-phenyl)carbonate], poly[1,1-cyclohexane bis(4-phenyl)carbonate] and the like; polysulfones; polyethers; polyketones; Polyamides such as poly(4-aminobutyric acid), poly(hexamethylene adipamide, poly(6-aminohexanoic acid), poly(m-xylylene adipamide), poly(p-xylylene sebacamide), poly(2,2,2-trimethylhexamethylene terephthalamide), poly(meta-phenylene isophthalamide) (NOMEX), poly(p-phenylene terephthalamide) (KEVLAR) and the like; polyesters such as poly(ethylene azelate), poly(ethylene 1,5-naphthalate), poly(1,4-cyclohexane dimethylene terephthalate), poly(ethylene oxybenzoate) (A-TELL), poly(para-hydroxybenzoate) (EKONOL), poly(1,4-cyclohexylidene dimethylene terephthalate) (KODEL) (eis), poly(1,4-cyclohexylidene dimethylene terephthalate) (KODEL) (trans), Polyethylene terephthalate, polybutylene terephthalate and the like; poly(arylene oxides) such as poly(2,6-dimethyl-1,4-phenylene oxide), poly(2,6-diphenyl-1,4-phenylene oxide) and the like; poly(arylene sulfides) such as poly(phenylene sulfide) and the like; polyetherimides; vinyl polymers and their copolymers such as polyvinyl acetate, polyvinyl chloride; polyvinyl butyral, polyvinylidene chloride, ethylene-vinyl acetate copolymers and the like; polyacrylics, Polyacrylate and their copolymers such as polyethyl acrylate, poly(n-butyl acrylate), polymethyl methacrylate, polyethyl methacrylate, poly(n-butyl methacrylate), poly(n-propyl methacrylate), polyacrylonitrile, water-insoluble ethylene-acrylic acid copolymers, water-insoluble ethylene-vinyl alcohol copolymers, acrylonitrile copolymers, methyl methacrylate-styrene copolymers, ethylene-ethyl acrylate copolymers, methacrylated butadiene-styrene copolymers and the like; polyolefins such as low density poly(ethylene), poly(propylene), chlorinated low density poly(ethylene), poly(4-methyl-1-pentene), poly(ethylene), poly(styrene) and the like; water-insoluble ionomers; poly(epichlorohydrins); Poly(urethane) such as the polymerization product of one or more diols such as ethylene glycol, propylene glycol and/or a polydiol such as diethylene glycol, triethylene glycol and/or tetraethylene glycol and the like with a diisocyanate such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and the like; and polysulfones such as the reaction product of the sodium salt of 2,2-bis(4-hydroxyphenyl)propane and 4,4'-dichlorodiphenylsulfone; furan resins such as poly(furan); cellulose ester plastic such as cellulose acetate, cellulose acetate butyrate, cellulose propionate and the like; Silicones such as poly(dimethylsiloxane), poly(dimethylsiloxane-co-phenylmethylsiloxane), and the like; protein plastics, and mixtures of two or more of the foregoing.

Vulcanizable and thermoplastic rubbers useful as matrix polymers and/or polymers or oligomers that can be sorbed to the surfaces of exfoliated phyllosilicate platelets can also vary widely in the practice of this invention. Illustrative of such rubbers are brominated butyl rubber, chlorinated butyl rubber, polyurethane elastomers, fluoroelastomers, polyester elastomers, polyvinyl chloride, butadiene/acrylonitrile elastomers, silicone elastomers, poly(butadiene), poly(isobutylene), ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, sulfonated ethylene-propylene-diene terpolymers, poly(chloroprene), poly(2,3-dimethylbutadiene), Poly(butadiene-pentadiene), chlorosulfonated poly(ethylene), poly(sulfide) elastomers, block copolymers constructed from segments of glassy or crystalline blocks such as poly(styrene), poly(vinyltoluene), poly(t-butylstyrene), polyesters and the like and the elastomeric blocks such as poly(butadiene), poly(isoprene), ethylene-propylene copolymers, ethylene-butylene copolymers, polyethers and the like such as the copolymers in poly(styrene)-poly(butadiene)-poly(styrene) block copolymer manufactured by Shell Chemical Company under the trade name KRATON®.

Useful thermosetting resins include, for example, the following: the polyamides; polyalkylamides, polyesters; polyurethanes; polycarbonates; polyepoxides and mixtures thereof.

Most preferred thermoplastic polymers for use as matrix polymers and/or polymers, oligomers that can be sorbed to the surfaces of exfoliated phyllosilicate platelets are thermoplastic polymers such as polyamides, polyesters, and polymers of α-β-unsaturated monomers and copolymers. Polyamides that can be used in the process of the present invention are synthetic linear polycarbonamides characterized by the presence of repeating carbonamide groups as an integral part of the polymer chain, separated from each other by at least two carbon atoms. Polyamides of this type include polymers commonly known in the art as nylon, obtained from diamines and dibasic acids, the repeating unit being represented by the following general formula:

-NHCOR¹³COHNR¹&sup4;-

wherein R¹³ is an alkylene group of at least 2 carbon atoms, preferably from about 2 to about 11, or arylene having at least about 6 carbon atoms, preferably from about 6 to about 17 carbon atoms; and R¹⁴ is selected from R¹³ and aryl groups. Also included are copolyamides and terpolyamides prepared by known methods such as for example, by condensation of hexamethylenediamine and a mixture of dibasic acids consisting of terephthalic acid and adipic acid. Polyamides of the above description are all well known in the art and include, for example, the copolyamide of 30% hexamethylene diammonium isophthalate and 70% hexamethylene diammonium adipate, poly(hexamethylene adipamide) (nylon 6,6), poly(hexamethylene sebacamide) (nylon 6,10), poly(hexamethylene isophthalamide), poly(hexamethylene terephthalamide), poly(heptamethylene pimelamide) (nylon 7,7), poly(octamethylene suberamide) (nylon 8,8), poly(nonamethylenazelamide) (nylon 9,9), poly(decamethylene sebacamide) (nylon 10,9), poly(decamethylene sebacamide) (nylon 10,10), poly[bis(4-amino-cyclohexyl)methane-1,10-decane-carboxamide)], Poly(m-xylylene adipamide), poly(p-xylylene sebacamide), poly(2,2,2-trimethylhexamethylene terephthalamide), poly(piperazine sebacamide), poly(p-phenylene terephthalamide), poly(meta-phenylene isophthalamide) and the like.

Other useful polyamides are those formed by polymerization of amino acids and derivatives thereof, such as lactams. Illustrative of these useful polyamides are poly(4-aminobutyric acid) (nylon 4), poly(6-aminohexanoic acid) (nylon 6), poly(7-aminoheptanoic acid) (nylon 7), poly(8-aminooctanoic acid) (nylon 8), poly(9-aminononanoic acid) (nylon 9), poly(10-aminodecanoic acid) (nylon 10), poly(11-aminoundecanoic acid) (nylon 11), poly(12-aminododecanoic acid) (nylon 12), and the like.

Preferred polyamides are poly(caprolactam), poly(12-aminodecanoic acid) and poly(hexamethylene adipamide).

Other matrix polymers (host polymers) and/or polymers that can be sorbed onto the surfaces of exfoliated platelets to form nanocomposites are linear polyesters. The type of polyester is not critical and the particular polyesters chosen for use in any particular situation will depend essentially on on the physical properties and characteristics, i.e., tensile strength, modulus, and the like, as desired in the final form. Consequently, a variety of linear thermoplastic polyesters having wide variations in physical properties are suitable for use in admixture with platelets of exfoliated layered material in the preparation of nanocomposites according to the present invention.

The particular polyester chosen for use may be a homopolyester or a copolyester or, if desired, blends thereof. Polyesters are typically prepared by the condensation of an organic dicarboxylic acid and an organic diol and the reactants may be added to the exfoliated platelets for in situ polymerization of the polyester while it is in contact with the platelets of exfoliated layered material after exfoliation of the phyllosilicate.

Polyesters suitable for use in this invention as matrix polymers and/or polymers or oligomers that can be sorbed to the surfaces of exfoliated phyllosilicate platelets are those derived from the condensation of aromatic, cycloaliphatic and aliphatic diols with aliphatic, aromatic and cycloaliphatic dicarboxylic acids and can be cycloaliphatic, aliphatic or aromatic polyesters.

Exemplary of useful cycloaliphatic, aliphatic and aromatic polyesters that can be used as matrix polymers and/or polymers or oligomers that can be sorbed to the surfaces of exfoliated phyllosilicate platelets in the practice of the present invention are: poly(ethylene terephthalate), poly(cyclohexylenedimethylene terephthalate), poly(ethylene dodecate), poly(butylene terephthalate), poly[ethylene(2,7-naphthalate)], poly(metha-phenylene isophthalate), poly(glycolic acid), poly(ethylene succinate), poly(ethylene adipate), poly(ethylene sebacate), poly(decamethylene azelate), poly(ethylene sebacate), poly(decamethylene adipate), poly(decamethylene sebacate), poly(dimethylpropiolactone). Poly(para-hydroxyhenxoal) (EKONOL). Poly(ethylene oxybenzoate) (A-tell), poly(ethylene isophthalate), poly(tetramethylene terephthalate), poly(hexamethylene terephthalate), poly(decamethylene terephthalate), poly(1,4-cyclohexane-dimethylene terephthalate) (trans), poly(ethylene-1,5-naphthalate), poly(ethylene-2,6-naphthalate), poly(1,4-cylcohexylidenedimethylene tere ephthalate), (KODEL) (ice) and poly(1,4-cyclohexylidenedimethylene terephthalate (KODEL) (trans).

Polyester compounds prepared from the condensation of a diol and an aromatic dicarboxylic acid are particularly suitable as matrix polymers and/or polymers or oligomers that can be sorbed to the surfaces of exfoliated phyllosilicate platelets of the present invention. Illustrative of such useful aromatic carboxylic acids are: terephthalic acid, isophthalic acid and o-phthalic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 1,1,3-trimethyl-5-carboxy-3-(p-carboxyphenyl)-idane, diphenyl ether-4,4'-dicarboxylic acid, bis-p-(carboxyphenyl)methane and the like. Of the above-mentioned aromatic dicarboxylic acids, those based on a benzene ring (such as terephthalic acid, isophthalic acid, orthophthalic acid) are preferred for use in the practice of this invention. Among these preferred acid precursors, terephthalic acid is a particularly preferred acid precursor.

The most preferred embodiments of the invention incorporating a polymer or oligomer on the surface of phyllosilicate platelets include a polymer selected from the group consisting of: poly(ethylene terephthalate), poly(butylene terephthalate), poly(1,4-cyclohexane-dimethylene terephthalate), a polyvinylimine, and a mixture thereof. Among these polyesters of choice, poly(ethylene terephthalate) and poly(butylene terephthalate) are most preferred.

Still other useful thermoplastic homopolymers and copolymers for forming the polymers or oligomers that adhere to the surfaces of the exfoliated Phyllosilicate platelets can be sorbed, and/or as matrix polymers for the formation of nanocomposites, are polymers obtained by polymerization of α-β-unsaturated monomers or the formula

R¹⁵R¹⁵O=CH⁺

are formed in which:

R¹⁵ and R¹⁶ are the same or different and are cyano, phenyl, carboxy, alkyl ester, halo, alkyl, alkyl substituted with one or more chloro or fluoro or hydrogen. Illustrative of such preferred homopolymers and copolymers are homopolymers and copolymers of ethylene, propylene, vinyl alcohol, acrylonitrile, vinylidene chloride, acrylic acid esters, methacrylic acid esters, chlorotrifluoroethylene, vinyl chloride and the like. Preferred are poly(propylene), propylene copolymers, poly(ethylene) and ethylene copolymers. More preferred are poly(ethylene) and poly(propylene).

In the preferred embodiments of the invention, the platelet-sorbed polymers and matrix polymers of choice in the preparation of nanocomposites are polymers and copolymers of olefins, polyesters, polyamides, polyvinylimines and blends thereof containing polyesters. In the most preferred embodiments of the invention, polymers and copolymers of ethylene, polyamides (preferably nylon 6 and nylon 66 and more preferably nylon 6) and blends thereof are used both for sorption to exfoliated platelet surfaces and as matrix polymers.

The mixture may include various optional components which may be additives commonly used with polymers. Such optional components include: nucleating agents, fillers, plasticizers, impact modifiers, chain extenders, plasticizers, dyes, mold release agents, antistatic agents, pigments, Fire retardants and the like. These optional components and appropriate amounts are well known to those skilled in the art.

The first step of exfoliating the layered material should involve delaminating at least about 99 wt.% of the phyllosilicate material to provide a nanocomposite composition comprising a matrix polymer with polymer-sorbed or oligomer-sorbed platelet particles substantially homogeneously dispersed therein.

The polymer-treated or oligomer-treated exfoliated platelet particles dispersed in matrix polymers as formed by this process have the thickness of the individual platelet layers and polymer or oligomer coatings.

The effect of incorporating into a matrix polymer the particulate dispersed nanoscale platelet particles polymer treated according to the invention is typically an increase in the tensile and tear modulus or an increase in the impact strength before fracture or glass transition temperature (Tg).

Molding compositions comprising a thermoplastic or thermosetting polymer containing a desired loading of polymer-sorbed or oligomer-sorbed platelets prepared in accordance with the invention are ideally suited for producing films and sheets having valuable properties. Such films and sheets can be molded by conventional methods such as vacuum processing or by hot pressing to form useful articles. The films and sheets of the invention are also useful as coating materials for other materials including, for example, wood, glass, ceramic, metal or other plastics, and exceptional strengths can be achieved using conventional adhesives such as those based on vinyl resins. The films and sheets can also be laminated with other plastic films, and this is preferably done by Coextrusion is achieved by bonding the films in a molten state.

The surfaces of the films and sheets, including those in the embossed form, can be improved or finished by conventional processes, such as by painting or by the application of protective films.

The polymer/platelet composites are particularly useful for making extruded films and film laminates, such as films for use in food packaging. Such films can be made using conventional film extrusion techniques. The films are preferably from about 10 to about 100 µm (microns), more preferably from about 20 to 100 µm (microns), and most preferably from about 25 to about 75 µm (microns) thick.

The homogeneously distributed polymer-treated or oligomer-treated platelet particles and matrix polymer that form nanocomposites are formed into a film by suitable film-forming processes. Typically, the composition is melted and forced through a film-forming die. The film of the nanocomposite may undergo steps to cause the platelets to further align such that the principal planes through the platelets are substantially parallel to the principal plane through the film. Biaxial stretching of the film is one method of accomplishing this. For example, the film is stretched in the axial or machine direction by tension rolls that pull the film as it is extruded from the die. The film is simultaneously stretched by clamping the edges of the film and pulling them apart in the transverse direction. Alternatively, the film is stretched in the transverse direction using a tubular film die and inflating the film as it passes out of the tubular film die. The films may have one or more of the following advantages: increased modulus; increased wet strength; increased dimensional stability; reduced moisture adsorption; reduced permeability to gases such as oxygen and liquids such as water, alcohols and other solvents.

The following specific examples are set forth to particularly illustrate the invention and are not to be construed as limitations thereon.

As shown in Examples 1 to 3 and 6 below, sodium bentonite was intercalated with solvent/water intercalating compositions using various organic solvents capable of solubilizing a subsequently added water-insoluble polymer, and after exfoliation of the clay, the platelets and tactoids were then contacted with the water-soluble polymer in the form of a polymer melt to adhere the polymer to the platelet surfaces with dehydration of the exfoliated platelets and without collapse of the platelets: EXAMPLE 1 (Fig. 4) I. Preparation of Gel A

II. Addition of water compatible solvent(s) and dehydration of gel

Premix the following; then add Gel A while stirring:

GBL-133,3g

DG - 133.3 g

Mix until thoroughly dispersed.

Then add 280 g of methyl ethyl ketone (MEK) (approximately 20%-30% of the total weight of Gel A plus H₂O-compatible solvent(s)) while stirring.

Apply heat at 80-100ºC until Gel A is dehydrated (to a moisture content of 0.5% or less).

Continue mixing the mixture the entire time. III. Preparation of polypropylene with isophorone and gel A Initial weight (%) Final weight (%)

An X-ray diffraction pattern for the material prepared by this Example 1 is shown in Figure 4. The width of the base of the peak at 13.03 Å (polypropylene) indicates that the exfoliated clay platelets and tactoids have an average thickness of 3.9 nm or 39 Å, suggesting that the exfoliate has an average number of three platelets with a polymer layer between each of the pairs of adjacent platelets.

The following examples and corresponding drawings show that the phyllosilicate (sodium bentonite) after water removal by contact with water and an organic solvent (Examples 5 and 6) is exfoliated and remains exfoliated; however, the phyllosilicate cannot be exfoliated without water (clay and organic solvent only - Example 4, Fig. 6); that the phyllosilicate can be exfoliated without the organic solvent (water only), but after dehydration the exfoliated platelets collapse back into the layered structure and show that after exfoliation with solvent and water, attempts to replace a water-insoluble polymer with the solvent adhering to the platelets by contacting the platelets with a polymer melt without the polymer melt including a solvent (at least about 25% by weight of the polymer) for the water-insoluble polymer (Example 5 - Fig. 9) is unsuccessful:

EXAMPLE 2 - (Fig. 5 AND 6) I. Exfoliating Belle Yellow Sodium Bentonite (Gel A)

A. In a 2000 ml beaker, add 100 ml of water, then using the Caframo blender with a 5.1 cm (2 inch) diameter blade, slowly add Belle Yellow (a teaspoonful, approximately 5 g) and 5 g of dimethyl sulfoxide (DMSO) to the water while mixing.

B. Adjust mixing speed if necessary to maintain optimal shear capacity because viscosity increases as Belle Yellow is incorporated into water and DMSO. The vortex should extend approximately 1/3 down the beaker if possible.

C. Shear the mixture for 1 hour until completely homogenized.

D. Take an X-ray scan of the gel to ensure exfoliation. (See Fig. 5).

II. Polymer + Nanocomposite

A. In a large stainless steel container add dimethyl sulfoxide (DMSO), Gel A (Belle Yellow + water) and ethylene vinyl alcohol polymer (EV-OH).

B. Using a hot plate, heat the reactants to 110ºC.

C. While the reactants are heating, shear and mix the gel into the polymer using the Coules mixer.

D. When the polymer is 100% melted, increase the mixer speed and shear the reactants to evaporate the water for at least 3 hours.

E. Stop the reaction, pour the products into bowls and let cool overnight.

F. Break the product into tiny pieces approximately 1-22 mm.

6. Rinse the finished polymer under running hot water until no trace of DMSO is left.

H. Conduct tests. (TGA (Thermogravimetric Analysis), X-ray, Clarity by microscope.

NOTE: For higher percentages of clay in polymer, adjust the ratio and incorporate the corrected amount into the reaction. For example, for a 10% concentration, 100 g of Belle Yellow and 900 g of EV-OH are used. The amount of solvent to use at this time is variable. A ratio of 5 wt% clay to 95 wt% water is preferred for preparing the gel. Of this ratio, a 50:50 H2O to DMSO is used, so for the 10% concentration, 1900 g H2O and 1900 g DMSO are used.

As shown in Figure 6, an X-ray diffraction pattern for the polymer-treated product across the height and width of the peak at 13.98 Å shows that the clay remains exfoliated and includes ethylene-vinyl alcohol polymer adhered to the platelet inner surfaces of the clay.

EXAMPLE 3 (Fig. 7) I. Exfoliating Belle Yellow Sodium Bentonite (Gel A)

A. In a 2000 ml beaker, add 100 ml of water, then using the Caframo blender with a 2 inch diameter blade, slowly add Belle Yellow (a teaspoonful, approximately 5 g) and 5 g of γ-butyrolactone (GBL) to the water while mixing.

B. Adjust mixing speed if necessary to maintain optimal shear capacity as viscosity increases as Belle Yellow is incorporated into water and GBL. The vortex should extend approximately 1/3 down the cup if possible.

C. Shear the mixture for 1 hour until completely homogenized.

D. Take an X-ray scan of the gel to ensure exfoliation. (See Fig. 2).

II. Polymer + Nanocomposite

A. In a large stainless steel container, add γ-butyrolactone (GBL), Gel A (Belle Yellow + water) and ethylene vinyl alcohol polymer (EV-OH).

B. Using a hot plate, heat the reactants to 110ºC.

C. While the reactants are heating, shear and mix the gel into the polymer using the Coules mixer.

D. When the polymer is 100% melted, increase the mixer speed and shear the reactants to evaporate the water for at least 3 hours.

E. Stop the reaction, pour the products into bowls and let cool overnight.

F. Break the product into tiny pieces approximately 1-22 mm.

G. Rinse the finished polymer under running hot water until no trace of GBL is present.

H. Perform tests. (TGA, X-ray, clarity by microscope).

NOTE: For higher percentages of clay in polymer, adjust the ratio and incorporate the corrected amount into the reaction. For example, for a 10% concentration, 100 g of Belle Yellow and 900 g of EV-OH are used. The amount of solvent to use at this time is variable. A ratio of 5 wt% clay to 95 wt% water is preferred for making the gel. Of this ratio, a 50:50 H₂O to GBL is used, so for the 10% concentration, 1900 g of H₂O and 1900 g of GBL are used.

As shown in Figure 7, an X-ray diffraction pattern for the polymer-treated product across the height and width of the peak at 15.976 Å shows that the clay remains exfoliated and includes ethylene-vinyl alcohol polymer adhered to the platelet inner surfaces of the clay.

EXAMPLE 4 (Fig. 8)

Example 2 was repeated without including the water (0% water) by exfoliating the clay to produce Gel A (using 70 wt% clay and 30 wt% DMSO based on the dry weight of the clay). As shown in Figure 8, the tall, narrow peak at 18.66 Å is indicative of sodium bentonite clay that was not exfoliated (or sodium bentonite clay that was exfoliated and then collapsed back into the original multilayered structure).

EXAMPLE 5 (Fig. 9)

Example 2 was repeated without a solvent or water, attempting to intercalate the EVOH polymer melt directly between the clay platelets. As shown in Figure 9, the clay was not intercalated (complexed with the EVOH polymer) and was not exfoliated. EXAMPLE 6 I. Preparation of Gel A

II. Addition of water compatible solvent(s) and dehydration of gel

Premix the following; then add Gel A while stirring:

GBL-133,3g

DG - 133.3 g

Mix until thoroughly dispersed.

Then add 280 g of methyl ethyl ketone (MEK) (approximately 20%-30% of the total weight of Gel A plus H₂O-compatible solvent(s)) while stirring.

Apply heat at 80-100 DC until Gel A is dehydrated (to a moisture content of 0.5% or less).

Continue mixing the mixture the entire time. III. Preparation of nylon 6,6 with γ-butyrolactone (GBL) and gel A Initial weight (%) Final weight (%)

Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be considered as illustrative only and is intended for the purpose of teaching those skilled in the art the best mode for carrying out the invention. The details of the structure may be varied considerably and the exclusive use of all modifications that come within the scope of the appended claims is reserved.

Claims (28)

1. Exfoliated platelets of a phyllosilicate material having a water-insoluble polymer electrostatically complexed to one or both of the important surfaces of said platelets without an onium ion or a silane coupling agent, said platelets being prepared by first exfoliating the phyllosilicate to form a gel comprising phyllosilicate platelets in a water/solvent mixture and then contacting the phyllosilicate platelets with a composition comprising a water-insoluble polymer and a solvent for said water-insoluble polymer. 2. Exfoliated platelets according to claim 1, wherein the concentration of water-insoluble polymer in said phyllosilicate-contacting composition is at least about 5% by weight. 3. Exfoliated platelets according to claim 2, wherein the concentration of water-insoluble polymer in said phyllosilicate-contacting composition is at least about 15% by weight. 4. Exfoliated platelets according to claim 3, wherein the concentration of water-insoluble polymer in said phyllosilicate-contacting composition is at least about 20% by weight. 5. Exfoliated platelets according to claim 4, wherein the concentration of water-insoluble polymer in said phyllosilicate-contacting composition is at least about 30% by weight. 6. Exfoliated platelets according to claim 5, wherein the concentration of water insoluble polymer in said phyllosilicate contacting composition is in the range of about 50 wt.% to 80 wt.%. 7. Exfoliated platelets according to claim 5, wherein the concentration of water insoluble polymer in said phyllosilicate contacting composition is in the range of about 50 wt.% to about 100 wt.%. 8. Exfoliated platelets according to claim 1, wherein the concentration of water-insoluble polymer in the composition contacting the phyllosilicate is initially at least about 16 weight percent based on the dry weight of the contacted phyllosilicate. 9. Exfoliated platelets according to claim 8, wherein the concentration of the polymer in the composition contacting the phyllosilicate is initially in the range of about 16 wt.% to about 200 wt.% based on the dry weight of the contacted phyllosilicate. 10. Exfoliated platelets according to claim 9, wherein the concentration of the polymer in the composition contacting the phyllosilicate is initially in the range of about 35 wt.% to less than about 55 wt.% based on the dry weight of the contacted phyllosilicate. 11. Exfoliated platelets according to claim 9, wherein the concentration of the polymer in the composition contacting the phyllosilicate is about 70% to about 200% by weight based on the dry weight of the contacted phyllosilicate. 12. Exfoliated platelets according to any one of the preceding claims, wherein the polymer has a weight average molecular weight in the range of about 225 to about 1,000,000 g/mol. 13. The exfoliated platelets of claim 12, wherein the polymer has a weight average molecular weight in the range of about 225 to about 10,000 g/mol. 14. Exfoliated platelets according to any one of the preceding claims, wherein the Phyllosilicate is exfoliated by forming a composition of the phyllosilicate, water and an organic solvent and shearing the composition to form a gel containing the exfoliated platelets having the organic solvent bound to a surface of the platelets. 15. Exfoliated platelets according to any one of the preceding claims, wherein the amount of polymer electrostatically complexed to the surfaces of the exfoliated platelets is from about 10% to about 80% by weight based on the dry weight of the exfoliated platelets. 16. Exfoliated platelets according to claim 15, wherein the amount of polymer electrostatically complexed to the surfaces of the exfoliated platelets is from about 15% to about 80% by weight based on the dry weight of the exfoliated platelets. 17. Exfoliated platelets according to claim 16, wherein the amount of polymer electrostatically complexed to the surfaces of the exfoliated platelets is from about 20% to about 70% by weight based on the dry weight of the exfoliated platelets. 18. Exfoliated platelets according to claim 17, wherein the amount of polymer electrostatically complexed to the surfaces of the exfoliated platelets is from about 20% to about 60% by weight based on the dry weight of the exfoliated platelets. 19. Exfoliated platelets according to claim 16, wherein the amount of polymer electrostatically complexed to the surfaces of the exfoliated platelets is from about 16% to about 80% by weight based on the dry weight of the exfoliated platelets. 20. Exfoliated platelets according to claim 19, wherein the amount of polymer electrostatically complexed to the surfaces of the exfoliated platelets is from about 16% to about 70% by weight based on the dry weight of the exfoliated platelets. 21. Nanocomposite comprising exfoliated platelets according to any one of the preceding claims admixed with a matrix polymer. 22. The nanocomposite of claim 21, wherein the matrix polymer is selected from the group consisting of: a polyamide; polyvinylimine; polyethylene terephthalate; polybutylene terephthalate; a polymer polymerized from a monomer selected from the group consisting of dihydroxyethyl terephthalate; hydroxyethyl terephthalate; dihydroxybutyl terephthalate, and mixtures thereof. 23. A process for producing polymer-bearing exfoliated platelets according to any of claims 1 to 20, comprising: exfoliating the phyllosilicate into phyllosilicate platelets by forming a composition of the phyllosilicate, water and an organic solvent and shearing the composition to form a gel containing the exfoliated platelets having the organic solvent electrostatically complexed to a surface of the platelets; and contacting the solvent-complexed exfoliated phyllosilicate platelets with a composition comprising a water-insoluble polymer or water-insoluble oligomer; and a solvent for said water-insoluble polymer or oligomer; and melting the water-insoluble polymer to drive off the complexed solvent and to complex the polymer to the phyllosilicate platelets. 24. The method of claim 23, further including the steps of: Combining the polymer-complexed platelets with a matrix polymer; and Dispersing said polymer-complexed platelets throughout said polymer. 25. The method of claim 23 or 24, wherein said polymer solvent comprises from about 50% to about 200% by weight of organic solvent based on the total weight of said composition contacting said phyllosilicate. 26. A method according to any one of claims 23 to 25, wherein the water-insoluble polymer carried by the exfoliated platelets has a functionality selected from the group consisting of: a carbonyl, hydroxyl, carboxyl, amine, amide, ether, ester, sulfate, sulfonate, sulfinate, sulfamate, phosphate, phosphonate, phosphinate and an aromatic ring. 27. A method for electrostatically adhering an organic liquid having a polar functionality to an inner surface of a phyllosilicate platelet, comprising: mixing the phyllosilicate with an intercalating composition comprising water and an organic solvent, wherein the water comprises at least about 4 wt.% based on the dry weight of the phyllosilicate and the organic solvent comprises at least 2 wt.% based on the dry weight of the phyllosilicate to form a gel; Dehydrating the gel to a water content of approximately 10% or less based on the dry weight of the phyllosilicate; and Mixing the dehydrated gel with a water-insoluble polymer and a solvent for said water-insoluble polymer. 28. The method of claim 27, further including the step of heating the mixture to a temperature sufficient to melt the water-insoluble polymer.